Optical Computer Made From Frozen Light

neutron_p writes "Scientists at Harvard University have shown how ultra-cold atoms can be used to freeze and control light to form the "core" - or central processing unit - of an optical computer. Optical computers would transport information ten times faster than traditional electronic devices, smashing the intrinsic speed limit of silicon technology. This new research could be a major breakthrough in the quest to create super-fast computers that use light instead of electrons to process information. Professor Lene Hau is one of the world's foremost authorities on "slow light". Her research group became famous for slowing down light, which normally travels at 186,000 miles per second, to less than the speed of a bicycle."

Comments

I am a skeptic

[Flywheels of Fire]

Most of the positive fanatics write lots of papers; those who think it's not going anywhere (like me) don't. There are sound physical reasons to be skeptical, in my mind:

1) Wavelengths are too big: 1 micron is now a large number, and optics doesn't work much smaller than this.

2) There are no good nonlinearities. Anyone can make a linear OR gate optically, but to function as an effective digital technology you need nonlinearity and level restoration. This is missing in pure optical systems, except at very high power levels. The high power levels imply low density. There are some optical gates which process data in "femtoseconds," but ask them how long it takes to get to the next gate. Maybe someday someone will invent a great, low power, fast, optically nonlinear material. Don't invest in it yet.

3) The serious workers are now mostly working in combined electronic/optical modes. The speeds here are limited by the gate speeds of the electronics, just like normal computers. You have to then ask if optics is a good (cost effective, space efficient, low power...) replacement for wire. Ultimately, the answer is probably yes, but there's an awful lot of work to do before that's true (for the distances of a few centimeters in high density computers, that is).

Re:I am a skeptic

[OneOver137]

1) Wavelengths are too big: 1 micron is now a large number, and optics doesn't work much smaller than this.

Please clarify what you mean here. 1 micron is in the IR, and optical laws work just fine down to fractions of an Angstrom as in Bragg diffraction and scattering of solids.

Re:I am a skeptic

[wwest4]

> those who think it's not going anywhere (like me) don't [write papers].
> There are sound physical reasons to be skeptical, in my mind:

No disrespect intended, but... having doubts is a lousy reason to be discouraged from research into this, or any, field. The reality is exactly the reverse: skepticism is a really good motivation to go and validate your assertions, instead of just keeping them unproven in your mind.

Speed of light

[dreadknought]

The speed of light is _only_ 186,000 mi/sec when traveling through a vacuum. Light travels at slower speeds through all other mediums (i.e. earth's atmosphere, glass, a super-cooled diamond, etc)

Adjusting definitions

[benhocking]

• Despite what the popular press might say, the speed of light has never been claimed to be a constant. The speed of light in a vacuum (c), however, is asserted to be a constant. Frozen light does not challenge this assertion at all.
• Instantaneous travel is impossible for the simple reason that "instantaneous" has no meaning. Quantum entanglement does not allow the transfer of information at faster-than-light speeds. It is worth noting that all kinds of things can travel faster than light (e.g., it is trival to show that shadows, humorously enough, can travel faster-than-light), but information is not one of those things.